SUBJECTS hydrochloric acid

Hydrochloric acid, ultrahigh purity. Subject hydrochloric acid (Ultrex, J. T. Baker) to sub-boiling distillation in a quartz still. 

If an appreciable amount of residue remains, note its colour. Add a few drops of water and test the solution (or suspension) with htmus or with Universal indicator paper. Then add a httle dilute hydrochloric acid and observe whether efiervesceiice occurs and the residue dissolves. Apply a flame test with a platinum wire on the hydrochloric acid solution to determine the metal present. (In rare cases, it may be necessary to subject a solution of the residue to the methods of qualitative inorganic analysis to identify the metal or metals present.) If the flame test indicates sodium, repeat the ignition of the substance on platinum foil. 

Methods (25,26) to iacrease the ratio of the desired a-isomer (1) versus the unsweet -isomer [22839-61-8] (3) exist and are proprietary. The isomers can be separated by subjecting the solution of the final step to hydrochloric acid. The desired a-isomer hydrochloride salt crystallines out of the solution the P-isomer remains. There are many patented synthetic processes. The large-scale synthesis of aspartame has been discussed (27—47). 

In water-wall incinerators. The internal walls of the combustion chamber are lined with boiler tubes that are arranged vertically and welded together in continuous sections. When water walls are employed in place of refrac toiy materials, they are not only useful for the recovery of steam but also extremely effective in controlling furnace temperature without introducing excess air however, they are subject to corrosion by the hydrochloric acid produced from the burning of some plastic compounds and the molten ash containing salts (chlorides and sulfates) that attach to the tubes. 

To produce a moulding composition, aniline is first treated with hydrochloric acid to produce water-soluble aniline hydrochloride. The aniline hydrochloride solution is then run into a large wooden vat and formaldehyde solution is run in at a slow but uniform rate, the whole mix being subject to continuous agitation. Reaction occurs immediately to give a deep orange-red product. The resin is still a water-soluble material and so it is fed into a 10% caustic soda solution to react with the hydrochloride, thus releasing the resin as a creamy yellow slurry. The slurry is washed with a counter-current of fresh water, dried and ball-milled. 

The mixture was poured in water, acidified to pH 1 with dilute hydrochloric acid, heated on the steam bath for 30 minutes and then subjected to steam distillation to remove the organic solvents. The residue was filtered, dried and recystallized several times from ethyl acetate. The A -19-nor-17a-ethinylandrosten-17/3-ol-3-one thus obtained had a MP of 198° to 200°C (in sulfuric acid bath), 200° to 204°C (Kofler). 

The viscous oil resin Is slurried twice with 250 cc portions of methanol to remove any unreacted primary amines. The oil residue after being washed with methanol is dissolved in ethyl alcohol and 75 cc of concentrated hydrochloric acid is added dropwise to the warm alcohol solution of the base. The dihydrochloride salts of the several hydroabietyl ethylenediamines precipitates immediately from solution. The salt is then separated by filtering and is washed twice with 100 cc portions of cooled ethyl alcohol. The dihydrochloride salts of the dehy-droabietyl, dihydroabietyl and tetrahydroabietyl ethylenediamine mixture have a melting point of about 292°C to 295°C. On subjecting the mixture to solubility analyses it Is found that the dehydroabietyl ethylenediamine is present in substantially the same proportion as is the dehydroabietylamine in the original "Rosin Amine D."... 

To a mixture of 7.5 parts by weight of 1,2,4-triethoxybenzene, 40 parts by volume of tetra-chloroethane and 7.5 parts by weight of succinic anhydride are added 23 parts by weight of anhydrous aluminum chloride. The mixture is stirred for 1 hour at 25°C and for another 2 hours at 60°C. After addition of 50 parts by weight of ice and 50 parts by volume of concentrated hydrochloric acid, the reaction mixture is subjected to steam distiilation. 

As further confirmation of this Rozenfeld has reviewed Russian work on this subject and reports that in pickling with sulphuric acid the amount of acid used in scale dissolution is only about one-tenth that consumed by the dissolution (corrosion) of the underlying metal. However, in hydrochloric acid the direct scale dissolution occurs to a much greater degree, and is responsible for about 40% of the acid consumption. 

For the preparation of standard cobalt solutions, use analytical grade cobalt(II) chloride or spectroscopically pure cobalt dissolved in hydrochloric acid subject solutions containing 0, 5, 10, 25, 50, 100, 150, and 200 jug of Co to the whole procedure. 

Procedure. Dissolve 0.1 g of the sample in 10 mL purified methanol and transfer 1.0 mL of this solution to a stoppered test-tube. Add 1.0 mL of solution A and one drop of concentrated hydrochloric acid, then place the stoppered tube in a beaker of boiling water for 5 minutes. Cool, and then add 5.0 mL of the potassium hydroxide solution. Measure the absorbance of the solution at 480 nm (blue-green filter) against a blank obtained by subjecting 1.0mL of purified methanol to the above procedure. 

The significantly lower dediazoniation rate of the l/f-3,5-dimethylpyrazole-4-di-azonium ion (8.22) compared with that of the benzenediazonium ion was the central subject of an MNDO study by Brint et al. (1985). The diazonium ion 8.22 has been recovered unchanged after heating for 3 h at 100 °C in aqueous hydrochloric acid. It is not completely decomposed after a similar treatment for 48 h (Reilly and Madden, 1925). Brint et al. calculated the heats of formation of this diazonium ion and of the corresponding heteroaryl cation 8.23 (Scheme 8-16). They found that the values of A//f for the diazonium ion 8.22 and for the benzenediazonium ion are almost identical, whereas that for the cation 8.23 is much greater. The energy required to dissociate the pyrazolediazonium ion is therefore nearly twice that required for the benzenediazonium ion (A//f = 329 and 194 kJ mol-1, respectively). 

Extraction procedures must be adjusted when separated anthocyanins will be tested in biological studies. We have found that the types of acids used for anthocyanin extraction as well as their residual concentrations in the final extract may affect the results obtained from biological tests. The growth inhibitory effect of anthocyanins on HT29 (human colonic cancer) cells may be overestimated if the residual acid in the extract exerts a toxic effect on the cells. Acetic acid residues in anthocyanin extracts showed less toxicity to HT29 cells than hydrochloric acid when samples were prepared under the same extraction procedure and subjected to the same tests on HT29 cells. In addition, the procedure to remove acids affected the acid residual concentration as well in final anthocyanin extracts, with lyophilization being more successful than rotary evaporation. 

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